1. Field of the Invention
The present invention relates to an earpiece and an electro-acoustic transducer.
2. Description of the Related Art
An electro-acoustic transducer such as an earphone drives a diaphragm according to an audio signal which is supplied from an audio reproducer, thereby generating an acoustic wave in the audible frequency range which corresponds to the audio signal. The generated acoustic wave is output to the external auditory canal of a user through an earpiece which is attached to the electro-acoustic transducer and vibrates the eardrum, so that it is transmitted as audio information.
An inner-type earphone with an earpiece attached at its end, for example, which is called an earplug-type earphone, is commercialized. The earpiece includes a tubular core portion which is attached to the end of an electro-acoustic transducer and extends in the output direction of an acoustic wave, and an external auditory canal fitting portion which is disposed outside of the core portion and fitted into the external auditory canal.
FIG. 7A shows an example of an earpiece 50 in which a core portion 52 and an external auditory canal fitting portion 56 are molded in one piece. In such kind of the earpiece 50, the core portion 52 and the external auditory canal fitting portion 56 are made of a single elastic material such as elastomer. Because the adhesive properties between the elastic material which forms the core portion 52 and the external auditory canal fitting portion 56 are poor, the integral molding which does not require the adhesive bonding is used.
FIG. 7B shows an example of an earpiece 60 in which a core portion 62 and an external auditory canal fitting portion 66 are molded as separate pieces. In such kind of the earpiece 60, the core portion 62 is made of a material with a relatively high hardness such as chloroethene, and the external auditory canal fitting portion 66 is made of a material with a moderate flexibility such as a cushioning material. Because a certain degree of bonding properties (adhesive properties) are assured between the members, the core portion 62 and the external auditory canal fitting portion 66 are molded as separate pieces and then bonded together.